This invention relates to the refining of hydrocarbons, and more particularly to the production of lubrication oils by catalytic hydrodewaxing.
In the production of lubricating oils, a petroleum refiner is often confronted with the problem of removing waxy paraffinic materials from hydrocarbon liquids which could otherwise be easily upgraded to lubricating oil base stocks and the like. The presence of the waxy paraffins is undesirable because they impart an unacceptably high pour point to the oil, thereby reducing the effectiveness of the oil under low temperature conditions.
The production of lubricating oils, therefore, often requires a process step for removing waxy paraffins, as for example by solvent dewaxing. Yet another method is catalytic dewaxing wherein the waxy feedstock, usually a waxy distillate obtained from a previous refining operation, is contacted with a suitable catalyst under conditions of elevated temperature and pressure so as to crack the waxy paraffins to other hydrocarbons having less effect upon the pour point. In general, the catalyst is highly selective for cracking the waxy components, and oftentimes the catalyst employed has hydrogenation activity such that, in the presence of hydrogen, the cracked components are essentially immediately saturated by hydrogenation. Dewaxing in this manner is usually referred to as "hydrodewaxing," and the catalyst employed is termed a hydrodewaxing catalyst.
Besides an acceptable pour point, the lubricating oil obtained from hydrodewaxing or other dewaxing operation must often meet or exceed established criteria, as for example, a specified viscosity index for the particular application in which the lubricating oil will find service. As a rule, the higher the viscosity index of a given lubricating oil, the more desirable it is, assuming that the viscosity index is increased without detrimentally affecting other desired properties of the oil.
Accordingly, it is a major object of the present invention to provide a novel catalytic hydrodewaxing process wherein a product lubricating oil of improved viscosity index is obtained without detrimentally affecting its other properties, as for example its pour point. It is yet another object of the invention to provide such a product in a high yield but with relatively low hydrogen consumption, even at relatively high operating temperatures. And it is a specific object of the invention to provide a novel hydrodewaxing process wherein the selectivity for an improved lubricating oil product is high, despite a relatively high operating temperature. These and other objects of the invention will become more apparent in view of the following description of the invention.